Questo lavoro è stato sostenuto da sovvenzioni NIH: HL671795, HL048743, e HL108630.

1. Preparazione di SDF-1α Glycan nanoparticelle Grazie allo scopo della fornitura in vivo, sterilizzare tutti i contenitori, pipette e puntali usati nella preparazione. <ol><li> Preparare le seguenti soluzioni madre in UltraPure Acqua: 1% di solfato di destrano; 1 M NaOH (sterile filtrata con una membrana PES); 0,1% chitosano in 0,2% di acido acetico glaciale (filtro attraverso 0,8 e 0,22 micron filtri consecutivamente e regolare il pH a 5,5 con NaOH in seguito); 0.1 M ZnSO4; 15% mannitolo; e 0,92 mg / ml SDF-1α (memorizzati in aliquote a 80 ° C, e conservato a 4 ° C una volta scongelati). </li><li> Sterilizzare soluzioni madre attraverso 0,22 micron membrane filtranti. Valutare i livelli di endotossine nella soluzione preparata con dosaggio limulus lisato di amebociti (LAL) gel coagulo. Assicurarsi che i livelli sono &lt;0,06 EU / ml. </li><li> Aggiungere 0,18 ml UltraPure acqua per un flaconcino di vetro da 1,5 ml contenente un bastoncino magnetico. Impostare la velocità scalpore a 800 giri al minuto. Aggiungere 0,1 ml 1%solfato destrano e mescolare per 2 minuti. Aggiungere 0,08 mg SDF-1α (0,087 ml di 0,92 mg / ml SDF-1α soluzione) e mescolare per 20 min. </li><li> Aggiungere 0,33 ml 0,1% chitosano, goccia a goccia e mescolare per 5 min. Cambio di velocità mescolare al massimo e aggiungere 0,1 ml 0,1 M ZnSO4 lentamente con una siringa da 0,1 ml (oltre 1 min). </li><li> Ritorna velocità mescolare a 800 giri al minuto e mescolare per 30 min. Aggiungere 0,4 ml 15% mannitolo e mescolare per 5 min. Trasferire la miscela di reazione in una provetta da 1,5 ml microcentrifuga. Centrifugare a 16.000 xga 4 ° C per 10 min. Nota: La presenza di mannitolo facilita la risospensione delle particelle dopo centrifugazione. A seconda della compattezza del pellet, la concentrazione mannitolo può essere variata da 0% al 5%. La completa risospensione delle particelle dopo ogni centrifugazione è fondamentale per evitare aggregati nella sospensione finale. </li><li> Aspirare il surnatante e utilizzare una pipetta per rimuovere l&#39;ultima goccia di liquido lentamente. Aggiungere 0,2 ml 5% mannitolo. Sospendere il pellet con 0,5 ml, 29 G neesiringa dle. Aggiungere 1 ml 5% mannitolo. Centrifugare a 16.000 xg per 15 min. </li><li> Ripetere il punto 1.6. </li><li> Aspirare il surnatante. Risospendere il pellet in 0,2 ml 5% mannitolo. Conservare la sospensione di particelle a 4 ° C. Nota: La sospensione di particelle può anche essere congelati a -80 ° C o liofilizzato. Compresi 5% mannitolo nella sospensione è essenziale per prevenire l&#39;aggregazione delle particelle dopo il congelamento e scongelamento o dopo liofilizzazione e reidratazione. Mannitolo può essere rimosso mediante centrifugazione della sospensione dopo lo stoccaggio. </li></ol> 2. Determinazione della dimensione delle particelle e Zeta Potenziale La dimensione delle particelle e il potenziale zeta sono analizzati mediante dynamic light scattering e light scattering elettroforetico, rispettivamente, con un analizzatore di particelle indicato nella Lista dei Materiali. <ol><li> Impostare i seguenti parametri per la misurazione delle dimensioni delle particelle: i tempi di accumulazione: 70; Tempi di ripetizione: 4; Temperatura: 25 ° C;Diluente: acqua; Regolazione Intensità: auto. </li><li> Diluire il campione di SDF-1α-DS-CS con acqua (diluizione 10 volte). Caricare 100 microlitri del campione ad una cuvetta UV monouso come una cuvetta Eppendorf. Inserire la cuvetta nel supporto cella. Attendere che la regolazione dell&#39;intensità di raggiungere &quot;Optimum&quot; (~ 10.000 cps). Avviare acquisizione dati. </li><li> Dopo la misurazione è completata, registrare i risultati cumulanti di diametro (nm) e l&#39;indice di polidispersità. Media dei risultati ottenuti da ciascuna delle 4 letture ripetute e calcolare la deviazione standard. </li><li> Carico 500 ml di 10 volte diluito campione di particelle ad una cella di flusso per la misura potenziale zeta. Impostare i seguenti parametri per la misurazione: i tempi di accumulazione: 10; Ripetere volte: 5; Temperatura: 25 ° C; Diluente: acqua; Regolazione Intensità: auto. Registrare i risultati del potenziale zeta (mV). Media la risultato di ciascuna delle 5 letture ripetute, e calcolare la deviatio serien. </li></ol> 3. Quantificazione di SDF-1α nelle particelle <ol><li> Diluire forma libera SDF-1α a concentrazioni di 0,01, 0,02, 0,03, 0,04, e 0,05 mg / ml in tampone 1.3x Laemmli. Diluire 6 microlitri campioni SDF-1α-DS-CS con 40 microlitri 1.3x tampone Laemmli. (Preparare 4x Laemmli scorta contenente 0,25 M Tris-HCl, pH 7.5, 8% SDS, 40% glicerolo, 0,05 mg / ml bromofenolo blu, e l&#39;8% 2-mercaptoetanolo. Dividere la soluzione di riserva in piccole aliquote e tenere a -20 ° C per uso singolo.) </li><li> Riscaldare i campioni a 100 ° C per 10 min. Vortex campioni due volte (ciascuno per 10 sec a velocità massima) durante il tempo di riscaldamento 10 min per dissociare completamente le particelle. Raffreddare i campioni a RT per 2 min. Centrifugare a 10.000 xg per 0,5-1 minuti per abbattere la condensa dell&#39;acqua. Nuovo Vortex per mescolare bene. Nota: A questo punto, la soluzione del campione deve essere chiaro senza alcun precipitato visibile presente. </li><li> Load 10 &amp;# 181; l campione / bene ad un gel SDS 4-20%. Eseguire elettroforesi a 200 V per 20 min. Colorare il gel con Coomassie macchia proteine ​​blu. </li><li> Esaminare la densità di banda della proteina di SDF-1α con un imager e analisi densitometria software molecolare. Calcolare la quantità di SDF-1α nelle particelle contro una curva standard costruita con connessione standard SDF-1α. </li></ol> 4. In Vitro saggio di rilascio <ol><li> Mescolare particelle glycan SDF-1α con tampone fosfato di Dulbecco senza calcio e magnesio (D-PBS) in un rapporto 1: 1 (v / v). </li><li> Dividere la sospensione di particelle in 0,05 ml aliquote in provette da 1,5 ml. Caricare i campioni al fondo delle provette. Evitare l&#39;introduzione di bolle d&#39;aria o disturbare la superficie del liquido. Sigillare la parte superiore dei tubi con Parafilm. NOTA: In tal modo, il liquido rimane sul fondo durante la successiva rotazione top-to-bottom del mixer tubo. </li><li> Ruotare i tubi a 37 &amp;# 176; C su un rotante Mixer Micro-Tube. Rimuovere aliquote dai tubi ai tempi indicati e centrifugare immediatamente i campioni a 16.000 xg per 10 min a 4 ° C. </li><li> Separare i supernatanti e pellet, e ricostituire il pellet con 0,05 ml di D-PBS. Conservare i campioni a -20 ° C. Dopo che tutti i campioni sono raccolti, esaminare i supernatanti e pellet su un gel SDS come descritto sopra. </li></ol> 5. Migration Assay Questo test misura l&#39;attività chemiotattica di SDF-1α. Interazione di SDF-1α con il suo recettore (CXCR4) sulla superficie cellulare provoca la migrazione della cellula verso il gradiente SDF-1α. In questo test, le cellule vengono caricati in un pozzo superiore (separati da una membrana semipermeabile da una minore ben) Soluzione e SDF-1α in un minor bene. <ol><li> Diluire SDF-1α (libero o di particelle-bound form) con tampone di migrazione (media RPMI-1640 contenente 0,5% di albumina sierica bovina) in un 3-fodiluizione in serie ld a concentrazioni finali di 100, 33, 11, 3,7, 1,2, 0,41, 0,14, e 0,05 ng / ml. </li><li> Aggiungere 0,6 ml della soluzione di SDF-1α diluito o tampone di migrazione solo (controllo negativo) per un pozzo nella piastra a 24 pozzetti. Aggiungere 0,57 ml di tampone di migrazione a un pozzo (controllo cella di input). Incubare a 37 ° C per 30 min. Inserire un permeabile inserto coltura cellulare come Transwell (dimensione dei pori 5 micron, Ø 6,5 mm) sulla parte superiore del pozzo inferiore. Carico 0,1 ml cellule Jurkat (5 × 10 5) nella Transwell inserire. Caricare 0,03 ml cellule direttamente al controllo cella di input bene. Incubare la piastra a 37 ° C per 2 ore in un incubatore CO 2 5%. </li><li> Rimuovere gli inserti Transwell. Trasferire le cellule che sono emigrati ai pozzetti inferiori ad una provetta di polistirene 4 ml. Contare le cellule migrate con citometro di flusso. </li><li> Calcolare la migrazione come percentuale del numero di cella di input (numero di cellule nel controllo cella di input ben x 100/30) dopo la sottrazione dei numeri in negative controlli (cellule migrate nei pozzetti contenenti solo buffer di migrazione). </li></ol>

<ol>
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The authors declare that they have no competing financial interests.

Come accennato in precedenza, le nanoparticelle DS-CS sono formati attraverso la neutralizzazione di carica tra polianione (DS) e policatione (CS) molecole. Poiché l&#39;interazione di carica avviene facilmente durante la collisione molecolare, la concentrazione delle soluzioni polimeriche e la velocità di agitazione durante la miscelazione è critica per la dimensione delle particelle risultanti. Una tendenza generale è che più diluita DS e CS soluzioni 15 e superiori risultato velocità di agitazione in...

Solfato Dextran (DS) e chitosano (CS) sono polisaccaridi con più sostituiti gruppi solfato carica negativa (a DS), o gruppi di ammine cariche positivamente (deacetilata CS). Quando miscelato in una soluzione acquosa, i due polisaccaridi formano complessi polielettroliti attraverso interazioni elettrostatiche. I complessi risultanti possono formare grandi aggregati che verrà a fasi separate dalla soluzione acquosa (precipitati), o piccole particelle che sono disperdibili in acqua (colloidi). Le condizioni specifiche che contribuiscono a questi risultati sono stati ampiamente studiati e sono stati riassunti ed illustrato in dettaglio in una recente revisione 1. Tra queste condizioni, due requisiti fondamentali per la produzione di particelle idrodispersibili sono i polimeri di carica opposta devono 1), una massa molare significativamente diverse; e 2) essere miscelato in un rapporto non stechiometrica. Queste condizioni permetteranno ai complessati segmenti polimerici carica neutrale generate dalla caricaneutralizzazione di segregare e formare il nucleo della particella, e il polimero in eccesso per formare il guscio esterno 1. Le particelle glycan descritti in questo protocollo sono destinati per la consegna polmonare, e sono progettati per essere al netto carica negativa, e di dimensioni nanometriche. La carica superficiale negativa riduce la probabilità di assorbimento cellulare delle particelle 2,3. Particelle di dimensioni nanometriche facilitano il passaggio attraverso le vie aeree distali. Per raggiungere questo obiettivo, la quantità di DS usato in questa preparazione è in eccesso di CS (rapporto in peso 3: 1); ed alto peso molecolare DS (medio ponderale Mw 500.000) e basso peso molecolare CS (MW 50-190 kDa, 75-85% deacetilato) sono utilizzati. SDF-1α è un fattore di homing delle cellule staminali, che esercita la funzione di riferimento attraverso la sua attività chemiotattica. SDF-1α svolge un ruolo importante in homing e manutenzione di cellule staminali ematopoietiche del midollo osseo, e nel reclutamento di progecellule Nitor per tessuti periferici per la riparazione del pregiudizio 4,5. SDF-1α ha un sito-eparina vincolante nella sua sequenza della proteina, che permette la proteina di legarsi all&#39;eparina / eparansolfato, formare dimeri, essere protetti da proteasi inattivazione (CD26 / DPPIV), e di interagire con le cellule bersaglio tramite i recettori della superficie cellulare 6-8. DS ha simili proprietà strutturali come eparina / eparansolfato; pertanto, il legame di SDF-1α DS sarebbe simile a quella dei ligandi polimerici naturali. Nella seguente protocollo, si descrive la preparazione di nanoparticelle SDF-1α-DS-CS. Le procedure rappresentano una delle formulazioni precedentemente studiate 9. Il protocollo è originariamente adattato da un&#39;indagine di nanoparticelle VEGF-DS-CS 10. Una piccola scala preparazione è descritta, che può essere facilmente scalata con le stesse soluzioni stock e condizioni di preparazione. Dopo la preparazione, le particelle sono caratterizzati by esaminando le loro dimensioni, potenziale zeta, estensione di incorporazione SDF-1α, tempo di rilascio in vitro, e l&#39;attività del incorporata SDF-1α.

<table border="0" cellpadding="0" cellspacing="0" width="489">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:255px;">Name</td>
			<td style="width:136px;">Company</td>
			<td style="width:99px;">Catalog number</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Dextran sulfate</td>
			<td>Fisher</td>
			<td>BP1585-100</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Chitosan, low molecular weight&#160;</td>
			<td>Sigma</td>
			<td>448869</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Zinc sulfate heptahydrate</td>
			<td>Sigma</td>
			<td>204986</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">D-Mannitol</td>
			<td>Sigma</td>
			<td>M9546</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">UltraPure water&#160;</td>
			<td>Invitrogen&#160;</td>
			<td>10977-023</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">SDF-1&#945;</td>
			<td>Prepared according to reference 8.</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Syringe filter, PES membrane 0.22 um.&#160;&#160;&#160;</td>
			<td>Millipore</td>
			<td>SLGP033RS</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Magnetic Micro Stirring Bars (2 x 7 mm)</td>
			<td>Fisher&#160;</td>
			<td>14-513-63</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Glass vial Kit; SUN-SRi</td>
			<td>Fisher&#160;</td>
			<td>14-823-182</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Delsa Nano C Particle Analyzer&#160;</td>
			<td>Backman Coulter</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Eppendorf UVette Cuvets</td>
			<td>Eppendorf</td>
			<td>952010069</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">4&#8211;20% Mini-PROTEAN TGX Gel</td>
			<td>Bio-Rad</td>
			<td>456-1096</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">GelCode Blue Safe Protein Stain</td>
			<td>Fisher&#160;</td>
			<td>PI-24592</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Molecular Imager VersaDoc MP 4000 System</td>
			<td>BioRad</td>
			<td>170-8640</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Corning Transwell Permeable Supports</td>
			<td>Corning</td>
			<td>3421</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Accuri C6 Flow Cytometer</td>
			<td>BD Biosciences</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dulbecco&#8217;s phosphate buffered saline&#160;</td>
			<td>Sigma</td>
			<td>D8537</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Pyrogent plus kit</td>
			<td>Fisher</td>
			<td>NC9753738</td>
		</tr>
	</tbody>
</table>

preparation and characterization of sdf-1&#945;-chitosan-dextran sulfate nanoparticles

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under appropriate conditions. The glycan nanoparticles are useful carriers for protein factors, which facilitate the in vivo delivery of the proteins and sustain their retention in the targeted tissue. The glycan polyelectrolyte complexes are also ideal for protein delivery, as the incorporation is carried out in aqueous solution, which reduces the likelihood of inactivation of the proteins. Proteins with a heparin-binding site adhere to dextran sulfate readily, and are, in turn, stabilized by the binding. These particles are also less inflammatory and toxic when delivered in vivo. In the protocol described below, SDF-1&#945; (Stromal cell-derived factor-1&#945;), a stem cell homing factor, is first mixed and incubated with dextran sulfate. Chitosan is added to the mixture to form polyelectrolyte complexes, followed by zinc sulfate to stabilize the complexes with zinc bridges. The resultant SDF-1&#945;-DS-CS particles are measured for size (diameter) and surface charge (zeta potential). The amount of the incorporated SDF-1&#945; is determined, followed by measurements of its in vitro release rate and its chemotactic activity in a particle-bound form.

La dimensione e il potenziale zeta delle particelle preparate SDF-1α-DS-CS sono determinate con un analizzatore di particelle. La Figura 1 mostra l&#39;analisi della misura di formato. Dai risultati ottenuti cumulanti quattro misurazioni ripetute, il diametro medio delle particelle idrodinamico SDF-1α-DS-CS è 661 ± 8.2 (nm) e la polidispersità è 0.23 ± 0.02. Il risultato della misurazione potenziale zeta è mostrato in Figura 2. Dalle cinque misurazioni ripetute, il potenziale ze...

Watch this Scientific Journal Video about Preparation and Characterization of SDF-1Î±-Chitosan-Dextran Sulfate Nanoparticles at JoVE.com

Preparation and Characterization of SDF-1&amp;#945;-Chitosan-Dextran Sulfate Nanoparticles

The objective of this protocol is to incorporate SDF-1&#945;, a stem cell homing factor, into dextran sulfate-chitosan nanoparticles. The resultant particles are measured for their size and zeta potential, as well as the content, activity, and in vitro release rate of SDF-1&#945; from the nanoparticles.

Preparazione e caratterizzazione di SDF-1α-Chitosan-Destrano solfato nanoparticelle

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under ...

preparation-characterization-sdf-1-chitosan-dextran-sulfate

Research

JoVE Journal

Chemistry

Preparation and Characterization of SDF-1&#945;-Chitosan-Dextran Sulfate Nanoparticles

12.3K Views.  Brigham and Women's Hospital and Harvard Medical School. The objective of this protocol is to incorporate SDF-1α, a stem cell homing factor, into dextran sulfate-chitosan nanoparticles. The resultant particles are measured for their size and zeta potential, as well as the content, activity, and in vitro release rate of SDF-1α from the nanoparticles.

Video: Preparation and Characterization of SDF-1&#945;-Chitosan-Dextran Sulfate Nanoparticles

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan &#948; solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials&#39; morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by St&#246;ber&#39;s methods, which have smooth surfaces.

Silica nanoparticles were prepared using acid-catalysis of a siloxane precursor and microwave-assisted synthetic techniques resulting in the controlled growth of nanomaterials ranging from 30-250 nm in diameter. The growth dynamics can be controlled by varying the initial silicic acid concentration, time of the reaction, and temperature of reaction.

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle ...

Ricerca

Chimica

Preparation and Characterization of Individual and Multi-drug Loaded Physically Entrapped Polymeric Micelles

Amphiphilic block copolymers like polyethyleneglycol-block-polylactic acid (PEG-b-PLA) can self-assemble into micelles above their critical micellar concentration forming hydrophobic cores surrounded by hydrophilic shells in aqueous environments. The core of these micelles can be utilized to load hydrophobic, poorly water soluble drugs like docetaxel (DTX) and everolimus (EVR). Systematic characterization of the micelle structure and drug loading capabilities are important before in vitro and in vivo studies can be conducted. The goal of the protocol described herein is to provide the necessary characterization steps to achieve standardized micellar products. DTX and EVR have intrinsic solubilities of 1.9 and 9.6 &#181;g/ml respectively Preparation of these micelles can be achieved through solvent casting which increases the aqueous solubility of DTX and EVR to 1.86 and 1.85 mg/ml, respectively. Drug stability in micelles evaluated at room temperature over 48 hr indicates that 97% or more of the drugs are retained in solution. Micelle size was assessed using dynamic light scattering and indicated that the size of these micelles was below 50 nm and depended on the molecular weight of the polymer. Drug release from the micelles was assessed using dialysis under sink conditions at pH 7.4 at 37 oC over 48 hr. Curve fitting results indicate that drug release is driven by a first order process indicating that it is diffusion driven.

The goal of this protocol is to describe the preparation and characterization of physically entrapped, poorly water soluble drugs in micellar drug delivery systems composed of amphiphilic block copolymers.

Preparazione e caratterizzazione di individuale e Multi-droga Loaded Fisicamente intrappolate polimerici Micelle

Amphiphilic block copolymers like polyethyleneglycol-block-polylactic acid (PEG-b-PLA) can self-assemble into micelles above their critical micellar ...

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

Sintesi, Caratterizzazione, e funzionalizzazione di ibrida UA / CdS e Au / ZnS core / shell nanoparticelle

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

Sintesi e caratterizzazione di supramolecolari colloidi

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, 1,4-benzene-bis(iminoguanidinium) (BBIG), is demonstrated. The ligand is synthesized as the chloride salt (BBIG-Cl) by in situ imine condensation of terephthalaldehyde with aminoguanidinium chloride in water, followed by crystallization as the sulfate salt (BBIG-SO4). Alternatively, BBIG-Cl is synthesized ex situ in larger scale from ethanol. The sulfate separation ability of the BBIG ligand is demonstrated by selective and quantitative crystallization of sulfate from seawater. The ligand can be recycled by neutralization of BBIG-SO4 with aqueous NaOH and crystallization of the neutral bis-iminoguanidine, which can be converted back into BBIG-Cl with aqueous HCl and reused in another separation cycle. Finally, 35S-labeled sulfate and &#946; liquid scintillation counting are employed for monitoring the sulfate concentration in solution. Overall, this protocol will instruct the user in the necessary skills to synthesize a ligand, employ it in the selective crystallization of sulfate from aqueous solutions, and quantify the separation efficiency.

A protocol for in situ aqueous synthesis of a bis(iminoguanidinium) ligand and its utilization in selective separation of sulfate is presented.

Separazione solfato da selettiva cristallizzazione con un legante bis-iminoguanidinium

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, ...

Preparation and In Vitro Characterization of Dendrimer-based Contrast Agents for Magnetic Resonance Imaging

Paramagnetic complexes of gadolinium(III) with acyclic or macrocyclic chelates are the most commonly used contrast agents (CAs) for magnetic resonance imaging (MRI). Their purpose is to enhance the relaxation rate of water protons in tissue, thus increasing the MR image contrast and the specificity of the MRI measurements. Current clinically approved contrast agents are low molecular weight molecules that are rapidly cleared from the body. The use of dendrimers as carriers of paramagnetic chelators can play an important role in the future development of more efficient MRI contrast agents. Specifically, the increase in local concentration of the paramagnetic species results in a higher signal contrast. Furthermore, this CA provides a longer tissue retention time due to its high molecular weight and size. Here, we demonstrate a convenient procedure for the preparation of macromolecular MRI contrast agents based on poly(amidoamine) (PAMAM) dendrimers with monomacrocyclic DOTA-type chelators (DOTA &#8211; 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate). The chelating unit was appended by exploiting the reactivity of the isothiocyanate (NCS) group towards the amine surface groups of the PAMAM dendrimer to form thiourea bridges. Dendrimeric products were purified and analyzed by means of nuclear magnetic resonance spectroscopy, mass spectrometry, and elemental analysis. Finally, high resolution MR images were recorded and the signal contrasts obtained from the prepared dendrimeric and the commercially available monomeric agents were compared.

Preparation and In Vitro Characterization of Dendrimer-based Contrast Agents for Magnetic Resonance Imaging

This protocol describes the preparation and characterization of a dendrimeric magnetic resonance imaging (MRI) contrast agent that carries cyclen-based macrocyclic chelates coordinating paramagnetic gadolinium ions. In a series of MRI experiments in vitro, this agent produced an amplified MRI signal when compared to the commercially available monomeric analogue.

Preparazione e<em&gt; In Vitro</em&gt; Caratterizzazione del dendrimero a base di agenti di contrasto per risonanza magnetica

Paramagnetic complexes of gadolinium(III) with acyclic or macrocyclic chelates are the most commonly used contrast agents (CAs) for magnetic resonance ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C60 molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C60/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C60 deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C60 chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C60 molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C60 chain structures to a hexagonal close packed quasi-1D stripe structure.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

Preparazione e caratterizzazione di nanostrutture ibride C60/Graphene

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution of capping ligands during the synthesis reaction, their role in regulating the nucleation and growth rates of colloidal nanoparticles is not well understood. In this work, we demonstrate a mechanistic investigation of the role of trioctylphosphine (TOP) in Pd nanoparticles in different solvents (toluene and pyridine) using in situ SAXS and ligand-based kinetic modeling. Our results under different synthetic conditions reveal the overlap of nucleation and growth of Pd nanoparticles during the reaction, which contradicts the LaMer-type nucleation and growth model. The model accounts for the kinetics of Pd-TOP binding for both, the precursor and the particle surface, which is essential to capture the size evolution as well as the concentration of particles in situ. In addition, we illustrate the predictive power of our ligand-based model through designing the synthetic conditions to obtain nanoparticles with desired sizes. The proposed methodology can be applied to other synthesis systems and therefore serves as an effective strategy for predictive synthesis of colloidal nanoparticles.

The main goal of this work is to elucidate the role of capping agents in regulating the size of palladium nanoparticles by combining in situ small angle x-ray scattering (SAXS) and ligand-based kinetic modeling.

Ligando-mediata di nucleazione e crescita di nanoparticelle metalliche Palladium

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution ...

High Resolution Physical Characterization of Single Metallic Nanoparticles

Individual molecules can be detected and characterized by measuring the degree by which they reduce the ionic current flowing through a single nanometer-scale pore. The signal is characteristic of the molecule&#39;s physicochemical properties and its interactions with the pore. We demonstrate that the nanopore formed by the bacterial protein exotoxin Staphylococcus aureus alpha hemolysin (&#945;HL) can detect polyoxometalates (POMs, anionic metal oxygen clusters), at the single molecule limit. Moreover, multiple degradation products of 12-phosphotungstic acid POM (PTA, H3PW12O40) in solution are simultaneously measured. The single molecule sensitivity of the nanopore method allows for POMs to be characterized at significantly lower concentrations than required for nuclear magnetic resonance (NMR) spectroscopy. This technique could serve as a new tool for chemists to study the molecular properties of polyoxometalates or other metallic clusters, to better understand POM synthetic processes, and possibly improve their yield. Hypothetically, the location of a given atom, or the rotation of a fragment in the molecule, and the metal oxidation state could be investigated with this method. In addition, this new technique has the advantage of allowing the real-time monitoring of molecules in solution.&#160;

Here, we present a protocol to detect discrete metal oxygen clusters, polyoxometalates (POMs), at the single molecule limit using a biological nanopore-based electronic platform. The method provides a complementary approach to traditional analytical chemistry tools used in the study of these molecules.

Caratterizzazione fisica ad alta risoluzione di nanoparticelle metalliche singole

Individual molecules can be detected and characterized by measuring the degree by which they reduce the ionic current flowing through a single ...

Synthesis and Characterization of Amphiphilic Gold Nanoparticles

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of their interactions with cell membranes, lipid bilayers, and viruses. The hydrophilic ligands make these particles colloidally stable in aqueous solutions and the combination with hydrophobic ligands creates an amphiphilic particle that can be loaded with hydrophobic drugs, fuse with the lipid membranes, and resist nonspecific protein adsorption. Many of these properties depend on nanoparticle size and the composition of the ligand shell. It is, therefore, crucial to have a reproducible synthetic method and reliable characterization techniques that allow the determination of nanoparticle properties and the ligand shell composition. Here, a one-phase chemical reduction, followed by a thorough purification to synthesize these nanoparticles with diameters below 5 nm, is presented. The ratio between the two ligands on the surface of the nanoparticle can be tuned through their stoichiometric ratio used during synthesis. We demonstrate how various routine techniques, such as transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and ultraviolet-visible (UV-Vis) spectrometry, are combined to comprehensively characterize the physicochemical parameters of the nanoparticles.

Amphiphilic gold nanoparticles can be used in many biological applications. A protocol to synthesize gold nanoparticles coated by a binary mixture of ligands and a detailed characterization of these particles is presented.

Sintesi e caratterizzazione delle nanoparticelle d'oro dell'anfifile

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of ...